The present project attempts to accomplish the following objectives: 1) Perform joint and tendon force analysis in normal and abnormal fingers and thumb. 2) Calculate the capsuloligamentous forces based on the joint resultant force and moment obtained. 3) Analyze the pathomechanics of finger and thumb through simulation study. 4) Perform objective functional evaluation of hand patients before and after treatment. 5) Correlate the theoretically calculated muscle force with its quantitative EMG. Normative models for the finger and thumb joints will be established based on biplanar x-ray method on marked cadaver specimens. An optimization method will be used in conjunction with the permutation/combination method for force calculation. Detailed cross-sectional studies are performed to construct the capsuloligamentous model and its force components will be determined by equipollent force analysis. Cadaver finger specimens will be tested under bending and torsions to assess the role of the ligaments and capsule in maintaining joint stability. Patients with pathological conditions will be evaluated functionally based on objective methods before and after various surgical or therapeutic managements. Integrated EMG of the extrinsic and intrinsic muscles will be measured while the hand is performing isometric activities. This information will be combined with the muscle physiological cross-sectional areas to provide the constraint relationships in the force analysis procedure based on optimization technique. Finally, the muscle EMG will be correlated with the theoretically predicted forces for qualitative verification.